In recent years much has been heard with respect to effects of environmental pollutants on various aspects of general health, and specifically on the respiratory tract, but there has been a modicum of experimental investigation into effects on resistance to airborne infection. Although several investigators have examined certain factors related to this general topic, none has performed in-depth, systematic investigations of multiple factors possibly involved in resistance to common respiratory tract pathogens after exposure to noxious air pollutants. The aims of the present proposal are: 1. To study the effects of nitrogen dioxide, carbon monoxide and lead oxides on handling aerosals of Streptococcus pneumoniae, Hemophilus influenzae and Pseudomonas aeruginosa by young male rats. This will include a study of in vivo pulmonary bactericidal capacity and non-viable particle clearance. 2. To study in vitro alveolar macrophage function in this model. 3. To study effects on pulmonary surfactant activity in this model system. These studies should provide a more rational basis for assigning a quantitative role to effects of air pollutants in lowering resistance to airborne infection.